Based On The New Control Strategy Of Unified Power Quality Controller Simulation And Experimental Study

With the development of science and technology, nonlinear load, large capacity surge load and fluctuating load are widely used in the power system, which bring about many power quality problems such as voltage harmonics, sags, fluctuations and flickers. Meanwhile, the devices which ask for high power quality are developed rapidly. These factors make the power grid suffer the rigorous test. The United Power Quality Conditioner (UPQC) is a power electronic device that can completely improve the power quality condition. It can compensate the harmonic and reactive current to prevent the power grid from being polluted, and it can also suppress the various voltage quality problems to provide high quality power for the customer.Breaking the tie of traditional way of thinking, the UPQC this paper studied employs the "direct control" strategy based on double close-loop control of voltage and current. Under this novel control strategy, the UPQC directly controls the power current to be the standard sinusoidal current synchronized with the grid voltage, and directly control the load voltage to be the rating sinusoidal voltage without complicated detection and calculation of harmonics. This paper presents two main theories on which the novel control strategy is based -"equivalence theory for APF compensation and current control" and "the theory for active power balance and DC-voltage balance". This paper designs the double close-loop controller. Simulation result verifies the validity of the UPQC under the novel control strategy.The single phase UPQC test equipment designed in this paper is constituted by two parts-main circuit and control circuit. The main circuit is composed of the following parts: the single phase bridge converter, the DC-capacitor, the series compensating transformer, the inductor for current tracking, the capacitor for filtering and etc. The control circuit is composed of main control board and current-controlling board.The main control board provides reference tracking current for the series and shunt part of the UPQC in which the TMS320LF2407A DSP is selected as the main processing microchip. This paper fulfills the following task: the DSP system design, generating standard sine wave synchronized with the grid voltage with regulable amplitude, PWM output design and over-voltage protection for IPM.The current-controlling part employs the "parabola PWM" method which can make the actual current track the reference current continually each cycle and to maintain the switching frequency to be nearly constant. This paper designed the implementing circuit for this method. Simulation and experimental results verify the effectiveness of the new current control method.The software design for DSP in this paper includes the software design for the above sine wave, A/D sampling and digital filter, the digital PID regulator and etc. The software is developed with mixed programming by C language and assembly language.Finally, this paper tests the UPQC equipment under different conditions and analyzes the experiment results. It concludes that the test equipment can fulfill the requested functions, but it still needs some improvement and further study.